A 4.1 W/mm2 Hybrid Inductive/Capacitive Converter for 2–140 mA-DVS Load under Inductor

This work presents a fully integrated hybrid inductive/capacitive converter maintaining high efficiency for a load range of 2 mA to 140 mA (70×) suitable for the dynamic voltage scaling (DVS) based loads. This high efficiency is achieved by using an inductive converter for higher loads (15–140 mA, 0.50–0.9 V) and a capacitive converter for lighter loads (2–5 mA, 0.40–0.55 V) with a 50 mV hysteresis margin. A digital state machine activates the appropriate converter based on the power efficiency and enables the converter hand-over. The functional feasibility of implementing digital circuits as representative loads under the inductor is shown thereby increasing the peak converter power density from 0.387 W/mm2 to 4.1 W/mm2 with only a minor hit on the efficiency. The maximum measured efficiency is achieved in inductive mode of operation and decreases from 76.4% to 71% when digital circuits are present under the inductor. The design was fabricated in IBM’s 32 nm SOI technology.